1. Field of the Invention
The present invention relates to a heat exchanger. More particularly, it relates to a method and apparatus for cooling contaminated water. Most specifically, it relates to a method and apparatus for cooling explosive-contaminated water using ambient temperature water circulated in two concentric cylinders and employing a brushing device to continually clean the cooling surfaces exposed to the contaminated water.
2. Description of Prior Art
The art of heat exchangers is well known as are techniques for maintaining efficient heat transfer characteristics of such devices under sustained operational use. In special applications, however, unique design problems arise creating unique and novel solutions. Treatment of very hot contaminated water containing contaminates that must be precipitated out by cooling prior to further treatment, e.g., explosive contaminats, is such a special application.
Generally, the art of heat exchangers deals with complicated tubular arrays wherein the tubular arrays transport the material to be heated/cooled through an enclosed heating/cooling medium. The tubes are then periodically cleaned by one of two processes. First the entire apparatus is shut down and the tubes cleaned by brushes, solvents, air pressure or the like. This is not desirable in the treatment of explosive contaminated water because the shut-down of the apparatus usually results in immediate further coating of the cold walls of the heat exchanger by the explosive contaminates. A second approach of conventional tubular arrays is to periodically inject plugs of some sort into the tubular flow path and having the plugs scrape away fouling on the inside of the tubes. In treatment of contaminated water wherein the stage immediately following the precipitation process caused by the heat exchanger is a filtration process, e.g., explosive-contaminated water, the plugs would soon block the filtration process and cause system shut down to remove the plugs or replace the filtration stage--resulting in the problem effects of the first approach.
Heat exchanger design specifically related to treatment of contaminated water where the contaminates are to be precipated out within the heat exchanger have generally been large complex installations having a common approach. This approach is to circulate a coolant through a pipe having a number of fins, bristles, or the like along its outer surface and to then move the pipe through the contaminated water or cause the contaminated water to circulate about the stationary pipe. The contaminates precipitate upon the projecting fins, bristles, spikes or the like until a sufficient amount accumulates on the projections. The heat exchanger is then shut down and the pipe withdrawn. Steam or water under pressure at approximately 180-200.degree. F. is injected onto the precipitate-coated projections causing melting and erosion of the precipitate. The waste water is then passed through a filter to remove pieces of precipitate. This conventional technique, called hot-water washout, has several shortcomings. First, the shut-down . . . start-up . . . shut-down cycle is slow and expensive to remove relatively small amounts of precipitate/cycle. Second, the shut-down of the exchanger causes immediate precipitate build-up on the inner-walls of the heat-exchanger, discussed supra, and necessitates including a sludge-pit beneath the heat exchanger that must be periodically scraped clean of the contaminates precipitated by shut-down. Third, the steam or hot water causes some of the contaminant to go back into solution thus negating some of the effect of both the heat-exchanger and the filter. Forth, adsorbtion beds usually receive water passing from the filter in conventional systems and the redissolved precipitate coming from the filter loads the adsorbtion bed with greater amounts of contaminate thus reducing the service life of the adsorbtion bed. Finally, many conventional systems, as a final stage, dump the remaining contaminated water into open pits allowing the water to leach and evaporate before covering the residue or allow the residue to dry and then burn it. Neither method is acceptable under present-day environmental standards.